[libcxx-commits] [libcxx] [libc++] P3391R2: `constexpr` integral overloads of `to_(w)string` (PR #205025)

[Nikolas Klauser via libcxx-commits]

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@@ -3798,17 +3804,88 @@ stoull(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI double stod(const wstring& __str, size_t* __idx = nullptr);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long double stold(const wstring& __str, size_t* __idx = nullptr);
 
+#    if _LIBCPP_STD_VER < 26 || defined(_LIBCPP_BUILDING_LIBRARY)
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(int __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned long __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long long __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned long long __val);
+#    endif // _LIBCPP_STD_VER < 26 || defined(_LIBCPP_BUILDING_LIBRARY)
+
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(float __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(double __val);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long double __val);
 #  endif // _LIBCPP_HAS_WIDE_CHARACTERS
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <class _String, class _Integer>
+_LIBCPP_HIDE_FROM_ABI constexpr _String __integer_to_string(_Integer __val) {
+  // numeric_limits::digits10 returns value less on 1 than desired for unsigned numbers.
+  // For example, for 1-byte unsigned value digits10 is 2 (999 can not be represented), so we need +1 here.
+  constexpr size_t __buf_size = numeric_limits<_Integer>::digits10 + 2; // +1 for minus, +1 for digits10
+  char __buf[__buf_size];
+  const auto [__ptr, __ec] = std::to_chars(__buf, __buf + __buf_size, __val);
+  _LIBCPP_ASSERT_INTERNAL(__ec == errc(), "__buf_size must be large enough to accommodate the value");
+  return _String(__buf, __ptr);
+}
+
+#    if !defined(_LIBCPP_BUILDING_LIBRARY)
+
+_LIBCPP_DIAGNOSTIC_PUSH
+#      if __has_warning("-Wgnu-inline-cpp-without-extern")
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wgnu-inline-cpp-without-extern")
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philnik777 wrote:

We will never care about this diagnostic, so we should disable it, not push/pop it.

https://github.com/llvm/llvm-project/pull/205025